Add abstract build method to MetricSnapshot.Builder (#969)

Signed-off-by: Mickael Maison <mickael.maison@gmail.com>

prometheus-metrics-model/src/main/java/io/prometheus/metrics/model/snapshots/CounterSnapshot.java

@@ -139,6 +139,7 @@ public Builder dataPoint(CounterDataPointSnapshot dataPoint) {
             return this;
         }
 
+        @Override
         public CounterSnapshot build() {
             return new CounterSnapshot(buildMetadata(), dataPoints);
         }

prometheus-metrics-model/src/main/java/io/prometheus/metrics/model/snapshots/GaugeSnapshot.java

@@ -118,13 +118,14 @@ private Builder() {
         }
 
         /**
-         * Add a data point. This can be alled multiple times to add multiple data points.
+         * Add a data point. This can be called multiple times to add multiple data points.
          */
         public Builder dataPoint(GaugeDataPointSnapshot dataPoint) {
             dataPoints.add(dataPoint);
             return this;
         }
 
+        @Override
         public GaugeSnapshot build() {
             return new GaugeSnapshot(buildMetadata(), dataPoints);
         }

prometheus-metrics-model/src/main/java/io/prometheus/metrics/model/snapshots/HistogramSnapshot.java

@@ -389,6 +389,7 @@ public Builder gaugeHistogram(boolean isGaugeHistogram) {
             return this;
         }
 
+        @Override
         public HistogramSnapshot build() {
             return new HistogramSnapshot(isGaugeHistogram, buildMetadata(), dataPoints);
         }

prometheus-metrics-model/src/main/java/io/prometheus/metrics/model/snapshots/InfoSnapshot.java

@@ -95,6 +95,7 @@ public Builder unit(Unit unit) {
             throw new IllegalArgumentException("Info metric cannot have a unit.");
         }
 
+        @Override
         public InfoSnapshot build() {
             return new InfoSnapshot(buildMetadata(), dataPoints);
         }

prometheus-metrics-model/src/main/java/io/prometheus/metrics/model/snapshots/MetricSnapshot.java

@@ -76,6 +76,8 @@ public T unit(Unit unit) {
             return self();
         }
 
+        public abstract MetricSnapshot build();
+
         protected MetricMetadata buildMetadata() {
             return new MetricMetadata(name, help, unit);
         }

prometheus-metrics-model/src/main/java/io/prometheus/metrics/model/snapshots/StateSetSnapshot.java

@@ -219,6 +219,7 @@ public Builder unit(Unit unit) {
             throw new IllegalArgumentException("StateSet metric cannot have a unit.");
         }
 
+        @Override
         public StateSetSnapshot build() {
             return new StateSetSnapshot(buildMetadata(), dataPoints);
         }

prometheus-metrics-model/src/main/java/io/prometheus/metrics/model/snapshots/SummarySnapshot.java

@@ -127,6 +127,7 @@ public Builder dataPoint(SummaryDataPointSnapshot data) {
             return this;
         }
 
+        @Override
         public SummarySnapshot build() {
             return new SummarySnapshot(buildMetadata(), dataPoints);
         }

prometheus-metrics-model/src/main/java/io/prometheus/metrics/model/snapshots/UnknownSnapshot.java

@@ -126,6 +126,7 @@ public Builder dataPoint(UnknownDataPointSnapshot data) {
             return this;
         }
 
+        @Override
         public UnknownSnapshot build() {
             return new UnknownSnapshot(buildMetadata(), dataPoints);
         }